The field of the invention is the production of synthetic resins having a six membered nitrogen ring with at least one diverse hetero atom and the invention is particularly concerned with the production of aqueous solutions of N-methylmorpholine-N-oxide.
U.S. Pat. No. 3,447,939 discloses the state of the art of using aqueous solutions of N-methylmorpholine-N-oxide and this disclosure is incorporated herein by reference.
N-methylmorpholine-N-oxide is shown by the disclosure of U.S. Pat. No. 3,447,939 to be a good solvent for cellulose and therefore is exceedingly well suited to the production of fibers.
Cellulose fibers made with N-methylmorpholine-N-oxide are characterized by improved tear resistance over conventional fibers.
Further applications of N-methylmorpholine-N-oxide are by-products for pharmaceutics. Because N-methylmorpholine-N-oxide evinces only a moderate storage stability and because as a pure substance it tends toward oxygen separation, the preferred commercial form is a 60% aqueous solution and furthermore it is used in this 60% aqueous solution.
However, storage stability and various applications require high solution purity. Contaminations which have been typically found and which degrade the storage stability or interfere in the application of N-methylmorpholine-N-oxide include N-methylmorpholine, peroxides and acid components. The impurities in the commercial products are noticeable by a deep yellow color.
The impurities can be detected analytically. Illustrative in the potentiometric titration of commercial N-methylmorpholine-N-oxide with hydrochloric acid and soda lye, two potential jumps are noted, which can be related to free methylmorpholine and carboxyl groups. Furthermore, peroxides are ascertained by iodometric titration, which because eluding precise identification, are calculated as being hydrogen peroxide.
Commercial N-methylmorpholine-N-oxide contains up to 1% by weight of methylmorpholine, up to 0.01% by weight of peroxides calculated as hydrogen peroxide, and up to 0.2% by weight of carboxyl groups. If according to the state of the art approximately equimolar amounts of (35%) hydrogen peroxide and (99%) commercial methylmorpholine are made to react, then there occurs a 57.4% solution of methylmorpholine-N-oxide comprising in its impurities 0.3% by weight of peroxide (calculated as H.sub.2 O.sub.2), 0.97% by weight of methylmorpholine and 0.3% by weight of carboxyl groups. After this solution is concentrated to the commercial solution of 60% by weight of methylmorpholine-N-oxide, the concentration of the impurities increases further, and therefore the product does not correspond to the state of the art. Because most of all the peroxide content is excessive, the literature suggests dissociating it by adding 0.1% by weight of catalase. This catalase, however, represents a further contaminant requiring in turn a subsequently costly purification comprising the following steps:
1. Removal of the water by azeotropic distillation with benzene. PA1 2. Separating the methylmorpholine-N-oxide phase from the benzene. PA1 3. Precipitating the methylmorpholine-N-oxide using acetone. PA1 4. Filtering and vacuum-drying the methylmorpholine-N-oxide. PA1 5. Preparing the solution.
This is a very costly procedure.